Composite ring seal and method of making

ABSTRACT

A radial loaded ring seal having an annular jacket of suitable material such as Teflon, the jacket being of channel-shaped cross section surrounding a loading spring of channel-shaped cross section, the loading spring being fabricated from a spring strip of suitable material such as stainless steel by being helically wound into a tube in which the edge margins of the successive convolutions are in overlapping relation, the tube then being formed into a ring and deformed under suitable pressure means in a die or by other suitable means into a generally U-shaped annular spring member having a double-walled channel with a radial side opening, after which the preformed jacket is applied to the spring to provide a composite structure in which the jacket forms a shield for the spring which in turn provides radial energizing means for the jacket.

0 United States Patent 1 1 3,561,776

[72] inventor John D. Wilson 3,223,426 12/1965 Reid 277/206X Pacific Palisades, Calif. 3,341.21 1 9/1967 Houghton et a1. 277/235X [21] Appl. No 777,227 3,357,693 12/1967 Perry 277/206X [22] Wed 1968 Primary Examiner-Charles .1. Myhre [451 Patented Att0rneyPaul A. Weilein [73] Assignee The Fluorocarbon Company Anaheim, Calif. awrlwrafion ofcalifflrma ABSTRACT: A radial loaded ring seal having an annular jacket of suitable material such as Teflon, the jacket being of l COMPOSITE RING SEAL AND METHOD OF channel-shaped cross sectlon surrounding a loading spring of M AKING channel-shaped cross sectlon, the loading spring being 23 claims 15 Drawing Figs fabncated from a s prlng strlp of sultable materlal suchas stainless steel by belng hellcally wound lnto a tube m which U-S. the edge margins of the uccessive convolutions are in over- 2 7/2l2, 277/235 lapping relation, the tube then being formed into a ring and [51] Int. Cl v F16] 15/32 deformed under uitable pressure means in a die or by other [50] Field 0 Search 277/152, uitable means into a generally U-shaped annular spring 1 2 1 235 member having a double-walled channel with a radial side opening, after which the preformed jacket is applied to the [56] References C'ted spring to provide a composite structure in which the jacket UNITED TE PATENTS forms a shield for the spring which in turn provides radial 3,1 14,561 12/ 1963 Creath et a1. 277/205X energizing means for the jacket.

We i 7 /0 BACKGROUND OF THE INVENTION The present invention relates to ring seals.

Heretofore, it has been known that the characteristics of certain plastic materials possess inherent properties which make them particularly advantageous for use as a sealing material. One of these is polytetrafluoroethylene resin, commonly known as 'Ieflon." Principally among the desirable characteristics of this material are its wide temperature range, chemical inertness, low friction, unlimited shelf life, high tensile and compressive strength, high wearability, and an ability of the material to seal by conforming to other surfaces. A desirable property which this material lacks, however, is that of elasticity, and for this reason it has not been possible to utilize it directly as a substitute for rubber and other elastomer types of seals where dependence upon natural resiliency is necessary to supply sufficient force at the interface of the seal and faying surface to effect sealing.

In order to overcome the lack of resiliency of Teflon, prior art structures have been designed with a loading spring which is arranged to artificially provide the resiliency which is lacking in the Teflon material. Such structures have been utilized in axially loaded seals, as well as in radially loaded seals. However, primarily due to the structural design of the spring element, the prior art devices have not been entirely successful for a wide range of installation conditions.

More specifically, it may be noted that in the case of axially loaded seals, one conventional construction has utilized a perforated U-shaped annular spring while another has utilized a V-shaped spring to energize a Teflon sealing surface. Seals of this type have been used in connection with pipe flange joints, fuel line connections, and similar installations. Use of either of these spring structures for a radial loaded seal is not practically possible as the stress characteristic is changed from essentially a beam loading in the axial loaded seal to a circumferential loading in a radial loaded seal. The spring operation is thus changed from a low stress/deflection to a high stress/deflection.

In the case of radial loaded seals, the trend has been to endeavor to design the loading spring so that it will embody a minimum of perforations, gaps, irregularities, or discontinuities, as well as high compliance (a low stress/deflection factor). Exemplary of springs which have been used in the radial loaded seal designs of the prior art is a helical wound, gartertype spring of wire or flat strip material. However, such springs have openings or gaps between the load applying surfaces engaged with the jacket. In other known designs of the prior art, a wire wound helical spring has been used. However, such a construction aggravates the condition. In still another design, a U-shaped spring has been used in which individual sections eliminate circumferential stresses, but still leave gaps and irregularities in the application of load to the jacket.

In the present invention, the inherent disadvantages of the prior art structures have been overcome by a unique spring design which eliminates openings and gaps and provides a relatively smooth loading surface, while at the same time enabling the use of a U-shaped section spring of generally conventional configuration but offering high compliance when utilized in a radial loaded orientation. Since the loading is substantially continuous, the spring of the present invention permits a thinner jacket than is possible in conventional designs. This is a vital advantage as in many applications it avoids the possibility of a thick jacket overpowering the spring under certain operating conditions which could cause a failure of the seal.

The spring structure of the present invention provides a longer jacket life in dynamic applications, and overcomes the disadvantages of springs of the prior art structure under static conditions where, for example, helical wound springs, particularly those utilizing wire, have been known to cut through the jackets. The spring structure of the present invention further pennits the fabrication of a radial loaded seal with a W cross section jacket which is particularly advantageous to form a shield over the spring as a protection against types of sealed media which would be damaging to the spring material. Further, in pharmaceutical and reagent chemical manufacturing, the jacket is "clean," easily rinsed, and not a source of entrapment for fluid which may later act as a contaminant. In the case of food processing, it is apparent that media such as milk cannot be sealed in commercial equipment with open spring seals, since this design does not insure complete removal of entrapped milk, even with steam cleaning.

SUMMARY OF THE INVENTION The present invention relates generally to scaling rings and is more particularly concerned with sealing rings of the type which are radially spring loaded, and an improved method for the fabrication thereof.

Having in mind the inherent disadvantages of the prior art structures as previously explained, it is one object of the herein-described invention toprovide a spring-loaded ring seal capable of utilizing a material such as Teflon and which will have low stress/deflection characteristics.

A further object is to provide a composite ring seal in which an annular sealing jacket is energized by a loading spring comprised of an imperforate helically wound strip in which the marginal edges of adjacent convolutions are in overlapping relation.

A further object is to provide a composite sealing ring ineluding an annular sealing jacket of Teflon or the like having a channel cross section and a helically wound imperforate loading spring having a channel cross section, and wherein the jacket provides a protective shield for the spring.

A still further object is to provide a composite ring seal structure in which the loading spring comprises a helically wound flat strip having edge margins of successive convolutions in overlapping relation so as to provide an imperforatc surface, and wherein the wound strip structure is deformed transversely into a channel configuration.

Another object is to provide a ring seal loading spring of helically wound construction which is transversely of channel configuration, and wherein the channel embodies double imperforate walls.

Still another object is to provide an improved method of fabricating an annular loading spring and associated jacket to provide a composite ring seal structure,

It is also an object to provide an improved imperforate helically wound ring seal loading spring, and method of fabricating the same.

Further objects and advantages of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing a preferred embodiment of the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the accompanying drawings, which are for illustrative purposes only:

FIG. 1 is a sectional view through a ring seal embodying the features of the present invention as it would appear when installed in a seal cavity;

FIG. 2 is an enlarged transverse sectional view through a strip such as used for fabricating the spring means embodied in the ring seal of the present invention;

FIG. 3 is an elevational view, partly in section of mechanism for winding the spring strip;

FIG. 4 is a sectional view of the same, taken substantially on line 4-4 of FIG. 3;

FIG. 5 is an enlarged view of the wound strip as it appears during the winding operation, portions being in section to show the overlap of the edge margins of the successive convolutions;

FIGS. 6, 7, and 8 are enlarged fragmentary perspective views showing the successive steps for joining the ends of a length of the helically wound strip to provide a ring configuration for the seal spring;

FIG. 9 is a sectional view taken substantially on line 9-9 of FIG. 8;

FIG. 10 is an enlarged plan view of the spring ring as it appears prior to deformation into its final channel configuration;

FIG. 11 is a view illustrating mechanism for deforming the spring ring, by means of cooperable die members shown in open position;

FIG. 12 is a fragmentary view showing the die members in closed position with the deformed ring therein;

FIG. I3 is an enlarged fragmentary perspective showing the channel configuration of the spring, including a transverse section therethrough to indicate the doublewalled structure thereof;

FIG. 14 is an enlarged fragmentary perspective view showing the preformed seal jacket as initially applied to the completed spring means during fabrication of the ring seal; and

FIG. is an enlarged fragmentary view illustrating the completed composite ring seal, a transverse section being taken therethrough for disclosing the cooperative association of the jacket and spring parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more specifically to the drawings, there is shown therein a composite sealing ring as generally indicated at 10 which embodies the features of the present invention and essentially includes a flexible annular jacket A and associated loading spring means B mounted in the jacket to reinforce and resist undue deformation thereof, as well as energize the jacket to assure a proper sealing action thereof.

As best shown in FIGS. I and 15, the jacket is constructed with a ring configuration having a channel-shaped cross section. More specifically, this jacket is fabricated so as to provide outer and inner circumferentially extending sidewalls Ila and llb which extend over the associated sidewalls 12a and 12b of the loading spring means B. The loading spring structure B, as in the case of the jacket, is of ring configuration with a channel cross section which is U-shaped, the sidewalls 12a and 12b being bridged by bottom wall portion 12c. As will be seen in FIG. I, the bottom wall portion of the loading spring means is intimately engaged by inwardly extending wall portions 13a and 13b which are integrally formed with the jacket sidewalls and extend inwardly into embracing engagement with the bridging wall portion of the loading spring means. At the opposite end, the sidewalls 11a and 1112 are interconnected by an integrally formed wall portion 11c, this portion being deflected between its ends so as to provide inner sidewalls 14a and 141; connected by a bridging wall 140 which are conformed to the inner wall surfaces of the loading spring means. As thus arranged, the loading spring means is of substantially U-shaped cross section, while the jacket is of substantially W-shaped cross section. Thus, the jacket provides a protecting shield for the spring means with respect to its side opening and prevents the sealed medium from coming into contact with the loading spring means. At this end of the jacket, the sidewalls 11a and Ilb are respectively provided with circumferentially extending sealing surface faces lSa and 15b which are adapted to engage circumferentially extending surfaces 160 and 16b which are to be sealed when the sealing ring is positioned within a seal cavity 17 which is in communication with a source of fluid pressure through an annular passage as indicated by numeral 18. The seal cavity is provided with a backup wall 19 which provides an abutment surface for circumferentially extending end faces 20a and 20b formed respectively on the wall portions 13a and 13b. Adjacent the surfaces 160 and 16b, the wall portions 13a and 13b have circumferentially extending surfaces 21a and 21b which are slightly recessed with respect to the sealing faces 15a and 15b so as to provide a small clearance.

It is preferred that the jacket A be formed ofa tough, dura blc, flexible material such as polytetrafluoroethylene resin, commonly known as Teflon" or some similar plastic material having the desired characteristics, and which will permit the fabrication of the jacket so as to have the preferred configura tion as explained above by using extrusion, molding, or machining processes as conventionally employed.

A main feature of the present invention resides in the unique construction embodied in the loading spring, and the method of its fabrication and embodiment into the composite sealing ring structure as described above. A most important factor contributing to the success of applicants sealing ring resides in a design concept which permits the utilization of a spring unit which embodies a helically coiled spring element in a manner whereby the inherent disadvantages of conventional arrangements will be successfully eliminated. It is believed that the construction of the loading spring unit will be best understood by explaining the method or manner of its fabricatron.

In the first instance, a strip 22 of flat ribbonlike material, for example, stainless steel or other suitable material is helically wound into the form of a flexible tube in such a manner that the marginal edges of successive convolutions will have overlapping relationship in which the leading edge 24 of each convolution will be outwardly exposed, while the trailing edge of the convolutions as indicated at 25 will be concealed by successive strip turns.

The mechanism for winding such a tube may vary as to details. One embodiment of a mechanism for this purpose is disclosed in FIGS. 3 and 4 as including a frame member 26 having edge seating flanges 27-27. An annular hub 26 on one side is positioned between these flanges and extends outwardly from a surrounding recessed planar surface 27a. An associated plate member 28 is provided with an opening 29 adapted to receive the hub thereinto to permit mounting of the plate 28 into assembled relation in face engagement with the seating flanges 27-27 in which position it can be secured by threaded screws 30. The hub 26' and associated plate 28 are provided with a series of aligned passages 31 which rotatably support a mandrel 32 therein. At one side of plate 28, the mandrel 32 extends through a winding passage 33 of sufficiently increased diameter to permit the winding of the tube structure 23 therein. At the inner end of the passage 33, the strip 22 is fed edgewise to the mandrel through the space 34 between the inner surface of plate 28 and the recessed planar surface 27a during a winding operation.

It has been found, however, that advantageous results are obtained and that it is possible to secure a smoother outer surface on the tube 23, if the leading edge 24 of the strip 22 is thinned by a stretching operation as shown in FIG. 2, prior to winding upon the mandrel. In the disclosed mechanism, this stretching and thinning operation is accomplished by carrying the entering strip edgewise around the hub 26' in an arcuate path as generally indicated at 35 so that the edge 24 of the entering strip will be radially outwardly positioned with respect to the edge 25.

Following the winding of the strip upon the mandrel, the wound strip is heated to a suitable temperature, for example, a temperature of the order of 900 F. in the case of stainless steel materials to relax the material and achieve a tightening of the winding. After treatment in this manner, the wound strip is removed from the mandrel, cleaned, and cut to required lengths.

The cut length of tube 23 is then formed into a circular or a ring configuration 36 (FIG. 10) by juxtaposing the opposite ends of the tube length, as shown in FIG. 6, wherein opposite ends of the strip, as indicated at 220 and 22b, are positioned so that upon telescoping the ends of the tubular structure, the strip ends 22a and 22b, may be easily guided and worked into an overlapping initial engagement, as shown in FIG. 7. By continuing to push the ends of the tube together, and the exercise of a slight twisting movement, the overlapped strip ends 220 and 22b may be caused to reach a desired fully lapped engagement as shown in FIGS. 8 and 9.

Having thus formed the ring configuration 36, this ring is now deformed into a channel configuration having a substantially U+shaped cross section. One mechanism for deforming the ring configuration 36 is disclosed in FIGS. 11 and 12 as comprising a lower female die member 37 and an operatively associated upper male die member 38, the die members being supported for relative movement to open and closed positions. The female die member is disclosed as having an annular groove 39 having an upwardly opening side defined by outer and inner concentric walls 401: and 40!) leading downwardly to downwardly converging sidewall portions 4la'and 41b respectively, which are interconnected at their lower extremities by a curved bottom wall 410. As thus arranged, a ring 36 may be placed in an initial position at the upper end of the annular groove between the concentric walls 40a and 40b.

The male die member 38 is provided with an appropriate annular projection 42 which isprovided at its base portion with inner and outer concentric wall portions 43a and 43b which lead to downwardly converging wall portions 440 and 44b, which terminate at their lower extremities in a curved end portion Me.

The annular groove 39 and annular projection 42 are so dimensioned that when the die members 37 and 38 are moved into closed position, as shown in H6. 12, the inserted ring 36 will be deformed into the bottom of the groove 39 in such a manner as to produce a double walled U -shaped channel configuration such as forms the loading spring means B of the composite sealing ring of the present invention. When deforming the ring 36, it is desirable to allocate the ring so that'the overlapped strip ends 22a and 22b will be positioned within the bottom of the channel as shown in FIG. 13. The overlapped ends are then spot welded together as indicated at 45.

The deformed, U-shaped spring structure is then passivated and is ready for assembly into the preformed jacket structure A as shown in FIG. 14 for the final assembly operation. With the jacket A and loading spring means B oriented as shown in FIG. 14, with the sidewalls 11a and llb of the jacket outwardly spaced with respect to the sidewalls 12a and 12b of the spring means, so that the wall portion 110 is of straight undeformed configuration, the assembled parts are placed in a suitable mold where they are heated to a temperature of sub stantially 250 F. and then cooled. During this operation the wall portion llc is deflected into the channel of the spring means, and the sidewalls 11a and llb moved into engaged position with the sidewalls 12a and 12b to provide the finished structure as shown in FIG. 15.

Although the ring seal has been described above as having the jacket A separately formed and assembled with the loading spring B, it is contemplated within the broad concept of the invention that the loading spring may have the sealing material applied directly as a surface coating or covering. The sealing material in such case would include any of a variety of materials such as plastics, metals, e.g., lead, and the like, which would be applied to the spring material either prior to or after the coiling operation.

From the foregoing description and drawings, it will be clearly evident that the delineated objects and features of the invention will be accomplished.

Various modifications may suggest themselves to those skilled in the art without departing from the spirit of the invention and, hence, I do not wish to be restricted to the specific form shown or uses mentioned, except to the extent indicated in the appended claims.

I claim:

l. A composite sealing ring, comprising:

a. an annular flexible sealing jacket of channel-shape in cross section formed to provide spaced opposed side walls; and

b. circumferentially extending spring loading means between said sidewalls, said spring means comprising a helically wound flat strip and being of generally channel shape configuration in cross section and formed to provide spaced opposed sidewalls respectively acting on said jacket sidewalls to resist deformation thereof.

2. A sealing ring according to claim 1, wherein the wound strip presents an impcrforate substantially smooth surface.

3. A sealing ring according to claim I, wherein the edge margins of successive convolutions of the wound strip are in overlapping relation.

4. A sealing ring according to claim 3', wherein the exposed overlapped edge is of less thickness than the concealed edge.

5. A sealing ring according to claim 1, wherein the spring means channel is substantially U-shaped and formed with a double wall.

6. As an article of manufacture, annular spring means. comprising:

a. a ring formed by a helically wound ribbonlike strip having overlapped convolutions, said wound strip having its opposite ends connected;

b. said ring having a double-walled U-shaped cross section including an inner wall and an outer wall; and

c. with the portions of the convolutions in one of said walls being oppositely inclined in relation to the portions of the convolutions in the other of said walls.

7. An article of manufacture according to claim 6, wherein the ring surface is' imperforate.

8. The method of fabricating a composite sealing ring. which comprises the steps of:

a. forming annular spring means of generally channelshaped cross section having a side opening and in which a helically wound ribbonlike strip of spring material has marginally material successive convolutions; and

b. thereafter conforming to the spring means a flexible sealing material to provide a ring jacket having a channelshaped cross section with channel wall portions respectively embracing opposed channel wall portions of the spring means.

9. The method according to claim 8, wherein the edge margins of successive convolutions are wound into overlapping relation.

10. The method according to claim 9, wherein the spring means presents a substantially smooth imperforate surface of engagement to the jacket.

1]. The method of fabricating a loading spring for a composite sealing ring, which comprises the steps of:

a. helically winding a ribbonlike strip of spring material into a tubular structure in which the edge margins of successive convolutions are in overlapped relation;

b. forming an elongate portion of the tubular structure into a ring configuration with the opposite ends of the portion juxtaposed; and

c. thereafter deforming the ring wall to obtain a ring configuration having a channel cross section.

12. The method according to claim ll, wherein the deformed ring wall provides a substantially U-shaped channel.

13. The method according to claim ll, wherein the ring channel is defined by a double wall.

14. The method according to claim 11, including the additional step of bonding the strip ends together at the juxtaposed ends of said portion.

15. The method according to claim I], wherein the edge of the wound strip which is outwardly exposed is of less thickness than the other edge, whereby the tubular structure will have a substantially smooth outer surface.

16. The method according to claim 11, wherein the ribbonlike strip prior to winding is stretched along its leading edge to decrease its thickness.

17. The method according to claim 16, wherein said leading edge is stretched by feeding the strip edgewise, prior to winding, over an arcuate path in which the leading edge is radially outwardly positioned with respect to the other strip edge.

18. The method according to claim 11, wherein the ring wall is die deformed to provide a double-walled circumferentially extending U-shaped channel having a radial open side.

19. A sealing ring, comprising:

a. annular spring means of U-shaped transverse section in- 22. A sealing ring according to claim 20, wherein the spring eluding a helically wound ribbonlike strip having overmeans has a substantially Ushapcd cross section with lapped convolutions coac ing to provid a l all in sidewalls extending from a bottom bridging portion and the Said sccl-ionian'j jacket sidewalls include portions overlapping said bottom b. a sealing medium overlying surfaces of the wound strip b id i portion on i inner d outer u facg5 adapted to sealingly engage a surface under the loading 23, A om osite sealing ring comprising:

Provided by Said 5PTing mean5- a. an annular flexible sealing jacket of channel-shape in A Composite Scalmg ""8 comprising: cross section formed to provide spaced opposed a. an annular flexible sealing jacket of channel-shape in sidewalls;

cfoss Section formed to provide Spaced Opposed b. circumferentially extending spring loading means sidewalls; between said sidewalls, said spring means being of clrcumferemlauy extendmg sprmg oadmg means generally channel shape configuration in cross section l l i z F spmfg w i of and formed to provided spaced opposed sidewalls respecgenera y 0 ape guratmn cross mono" tively acting on said jacket sidewalls to resist deformation and formed to provide spaced opposed sidewalls respecthereof. and

tively acting on said acket sidewalls to resist deformation c said jacket channel being substantially w shapcd and the thereof; and I g j c. said jacket sidewalls having inner and outer wall portions i a h g i z g embracing and shielding the spring means in an operative i e .Sprmg mcdlis emg n e i e sides of said channels in confronting relation, and the position from the sealed medium. i 21. A sealing ring according to claim 20, wherein the jacket Jacket wan Pomons embracmg and shleldmg the Sprmg means in an operative position from the sealed medium outer wall portions have circumferentially extending outer sealing faces.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 561,776 Dated February 9, 1971 Inventofls) v I II U Q fiilson It. is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column 6, line 28, "material" should read "engaged".

Signed and sealed this 13th day of July 1971.

(SEAL) Attest:

EDWARD H.FLETCHER,J'R. WILLIAM E. SCHUYLER, JR. Atteating Officer Commissioner of Patents 

1. A composite sealing ring, comprising: a. an annular flexible sealing jacket of channel-shape in cross section formed to provide spaced opposed side walls; and b. circumferentially extending spring loading means between said sidewalls, said spring means comprising a helically wound flat strip and being of generally channel shape configuration in cross section and formed to provide spaced opposed sidewalls respectively acting on said jacket sidewalls to resist deformation thereof.
 2. A sealing ring according to claim 1, wherein the wound strip presents an imperforate substantially smooth surface.
 3. A sealing ring according to claim 1, wherein the edge margins of successive convolutions of the wound strip are in overlapping relation.
 4. A sealing ring according to claim 3, wherein the exposed overlapped edge is of less thickness than the concealed edge.
 5. A sealing ring according to claim 1, wherein the spring means channel is substantially U-shaped and formed with a double wall.
 6. As an article of manufacture, annular spring means, comprising: a. a ring formed by a helically wound ribbonlike strip having overlapped convolutions, said wound strip having its opposite ends connected; b. said ring having a double-walled U-shaped cross section including an inner wall and an outer wall; and c. with the portions of the convolutions in one of said walls being oppositely inclined in relation to the portions of the convolutions in the other of said walls.
 7. An article of manufacture according to claim 6, wherein the ring surface is imperforate.
 8. The method of fabricating a composite sealing ring, which comprises the steps of: a. forming annular spring means of generally channel-shaped cross section having a side opening and in which a helically wound ribbonlike strip of spring material has marginally material successive convolutions; and b. thereafter conforming to the spring means a flexible sealing material to provide a ring jacket having a channel-shaped cross section with channel wall portions respectively embracing opposed channel wall portions of the spring means.
 9. The method according to claim 8, wherein the edge margins of successive convolutions are wound into overlappIng relation.
 10. The method according to claim 9, wherein the spring means presents a substantially smooth imperforate surface of engagement to the jacket.
 11. The method of fabricating a loading spring for a composite sealing ring, which comprises the steps of: a. helically winding a ribbonlike strip of spring material into a tubular structure in which the edge margins of successive convolutions are in overlapped relation; b. forming an elongate portion of the tubular structure into a ring configuration with the opposite ends of the portion juxtaposed; and c. thereafter deforming the ring wall to obtain a ring configuration having a channel cross section.
 12. The method according to claim 11, wherein the deformed ring wall provides a substantially U-shaped channel.
 13. The method according to claim 11, wherein the ring channel is defined by a double wall.
 14. The method according to claim 11, including the additional step of bonding the strip ends together at the juxtaposed ends of said portion.
 15. The method according to claim 11, wherein the edge of the wound strip which is outwardly exposed is of less thickness than the other edge, whereby the tubular structure will have a substantially smooth outer surface.
 16. The method according to claim 11, wherein the ribbonlike strip prior to winding is stretched along its leading edge to decrease its thickness.
 17. The method according to claim 16, wherein said leading edge is stretched by feeding the strip edgewise, prior to winding, over an arcuate path in which the leading edge is radially outwardly positioned with respect to the other strip edge.
 18. The method according to claim 11, wherein the ring wall is die deformed to provide a double-walled circumferentially extending U-shaped channel having a radial open side.
 19. A sealing ring, comprising: a. annular spring means of U-shaped transverse section including a helically wound ribbonlike strip having overlapped convolutions coacting to provide a doublewall in said section; and b. a sealing medium overlying surfaces of the wound strip adapted to sealingly engage a surface under the loading provided by said spring means.
 20. A composite sealing ring, comprising: a. an annular flexible sealing jacket of channel-shape in cross section formed to provide spaced opposed sidewalls; b. circumferentially extending spring loading means between said sidewalls, said spring means being of generally channel-shape configuration in cross section and formed to provide spaced opposed sidewalls respectively acting on said jacket sidewalls to resist deformation thereof; and c. said jacket sidewalls having inner and outer wall portions embracing and shielding the spring means in an operative position from the sealed medium.
 21. A sealing ring according to claim 20, wherein the jacket outer wall portions have circumferentially extending outer sealing faces.
 22. A sealing ring according to claim 20, wherein the spring means has a substantially U-shaped cross section with sidewalls extending from a bottom bridging portion, and the jacket sidewalls include portions overlapping said bottom bridging portion on its inner and outer surfaces.
 23. A composite sealing ring, comprising: a. an annular flexible sealing jacket of channel-shape in cross section formed to provide spaced opposed sidewalls; b. circumferentially extending spring loading means between said sidewalls, said spring means being of generally channel shape configuration in cross section and formed to provided spaced opposed sidewalls respectively acting on said jacket sidewalls to resist deformation thereof; and c. said jacket channel being substantially W-shaped and the spring means channel being substantially U-shaped, the jacket and spring means being mounted with the open sides of said channels in confronting relation, and the jacket wall portions embracing and shielding the spring means in an operative positiOn from the sealed medium. 